Static locals requiring initialization are not thread safe on Windows.
Unfortunately, it's possible to create static locals that are actually
externally visible with inline functions and templates. As a result, we
have to implement an initialization guard scheme that is compatible with
TUs built by MSVC, which makes thread safety prohibitively difficult.
MSVC's scheme is that every function that requires a guard gets an i32
bitfield. Each static local is assigned a bit that indicates if it has
been initialized, up to 32 bits, at which point a new bitfield is
created. MSVC rejects inline functions with more than 32 static locals,
and the externally visible mangling (?_B) only allows for one guard
variable per function.
On Eli's recommendation, I used MangleNumberingContext to track which
bit each static corresponds to.
Implements PR16888.
Reviewers: rjmccall, eli.friedman
Differential Revision: http://llvm-reviews.chandlerc.com/D1416
llvm-svn: 190427
Summary:
This also relaxes the requirement on Windows that the member pointer
class type be a complete type (http://llvm.org/PR12070). We still ask
for a complete type to instantiate any templates (MSVC does this), but
if that fails we continue as normal, relying on any inheritance
attributes on the declaration.
Reviewers: rjmccall
CC: triton, timurrrr, cfe-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D568
llvm-svn: 178283
Reid Kleckner